Author: see_sharp_dotnet

I purchased a Motorola CDM1250 a while ago and finally got around to installing it in my 2103 F-150. Here’s the final result:

This radio is a GMRS radio – it’s is kinda like CB, but operating on higher frequencies and with more output power. In addition to the greater allowed power, another advantage of GMRS over CB is the ability to access repeaters. For those who aren’t familiar, a repeater extends the range of mobile radios with a radio and large antenna (usually on a mountain top, a tower, or building roof) that re-transmits your audio over a large area. 50-100 mile range between radios is common when using a repeater.

I mainly use GMRS when traveling highways or when camping and off-roading. I’m also part of a GMRS club that maintains repeaters for use by club members. There are also many owner-operated repeaters across the country which are open for use by the general public, check out mygmrs.com. This radio is also compatible with the cheap “bubble pack” walkie-talkies you can get at Wally World for close range trail comms. An FCC license is required to operate at the higher power and access repeaters in the GMRS band, however no test is required and the license is valid for 10 years. Get your GMRS license here!

I chose to install the radio in the center console, so I made a mount from some 3/4″ MDF and some 1″ pine:

I laid on a few coats of Krylon textured flat black paint after a quick test fit. The whole unit drops in and out of the center console easily and fits snugly inside. To power the radio (and future radios) I installed a 50A sub panel inside the center console. I ran 10ga wire from the battery, through the firewall, and up the transmission hump to get power to the panel:

For now I’m running a mag mount with a 5/8 wave antenna. My truck has a sunroof which complicates antenna placement a little bit. My work also has underground parking, and the truck has about 1″ of clearance with the stock ride height. Any roof mounted antenna will be damaged if it is not removed before entering the garage. Not sure what I want to do about that yet… I’m also planning on installing a scanner in the console as well, using a front fender mounted antenna placed near the stock AM/FM antenna which I have removed.

I came across a post on reddit last week that had a link to receive a free poster illustrating electromagnetic spectrum allocation, courtesy of a company called Textronix, a testing and measurement instrument manufacturer based in Mesa, AZ (no affiliation with me). It’s pretty neat – I received mine in the mail today and just wanted to share some pictures here:

I was going to share the link to order the poster when I started this post, but it looks like that link has since 404’d, likely due to the high volume of requests. A downloadable PDF version of the poster is available here:

I recently wrote a review of the BTECH GMRS-V1 handheld radio for my club’s forum, but I would like to share it here as well. I was in the market for a handheld GMRS radio to be used primarily for outdoor recreation – mountain biking, camping, hiking, fishing, etc, so I’d like to share a quick review here. I had a few requirements of the radio before purchase: the radio should be affordable (< $100), have keypad programming, have a lightweight and compact design, and most importantly, the radio should be FCC Part 95 certified. After scouring the interwebs and reading about all sorts of different HTs, I settled on the BTECH GMRS-V1 (FCC ID: 2AGND-GMRS-V1):

The cheap Chinese radios that have flooded the market in recent years have elicited mixed feelings from hams and other radio folks, so I was a bit skeptical at first. Because some of these radios lack any type-acceptance and can be capable of transmitting all across the VHF and UHF spectrum, they are often associated with illegal activities – on both sides of the law. But the BTECH GMRS-V1 is not one of them, it is a purpose-made GMRS radio. It is actually a Baofeng UV-82 re-purposed for transmitting on GMRS frequencies only. GMRS Channels 1-7 and 15-22 are hard coded into the transceiver. An additional 8 channels with a +5 MHz repeater offset are also hard coded into the radio. Here is the complete list of pre-programmed frequencies and channel assignments in the radio:

Programming this radio is done via the keypad, the manufacturer’s software, or via 3rd party software, CHIRP. The manufacturer’s software works, but is a bit clunky to use. CHRIP is an excellent alternative, and has a large user base to provide support and help answer questions. I had zero issues programming this radio using CHRIP and Kenwood-style programming cable. Unlike some of the newer Uniden GMRS offerings, this radio will do split TX and RX tones. The included user manual for this radio is actually useful, unlike some Chinese radios. The manual was written in English (not translated) and clearly explains every feature of the radio. Some reviewers have reported the user interface to be unintuitive and/or difficult to use compared to other manufacturer’s radios, but I did not find this to be the case. I’m the type of person who always RTFM, so I had no problems getting up and running with the radio very quickly.

The fact that the channels are pre-programmed and cannot be modified can be a turn-off to some users, but this appears necessary to gain the FCC Part 95A certification. This is not a huge drawback for me, however. When I’m using this radio I’m usually just on a single channel for simplex or monitoring a single repeater. The TX and RX tones can be easily set from the keypad, and I’m ready to go. As far as the construction of the radio goes, it is made of plastic, but it does feels solid. There are no parts on the radio that look particularly cheap or may easily break. The belt clip could maybe be a little beefier, but it works just fine. It’s definitely not heavy duty like a top of the line Motorola HT, but I think this radio could survive a couple falls to the ground should I drop it or it pops off my backpack on a bike ride. And if the radio does break, I’m only out $50.

Radio performance I’ve found to be excellent. Reception with the included antenna was surprisingly good, though audio does get a bit distorted at the highest volume. I was sitting on top of a butte in Papago Park in Tempe a few weeks ago, monitoring the PHX 550 repeater with my Uniden BC125AT and the BTECH GMRS-V1. The Uniden scanner has a fairly decent antenna, a Diamond dual band high gain antenna, but the 550 repeater would often not break the squelch. The GMRS-V1 however, was receiving the 550 repeater loud and clear all over the park. Transmission was also equally impressive. From the top of South Mountain I was easily able to hit all the area repeaters. I have received signal reports from a few AGRC members and others that my transmission was loud and clear. The HT also works surprisingly well from inside my truck. With a relatively clear line of sight to the White Tanks from various spots on the freeways, I’m able to transmit and receive from the 550 repeater with ease. Outside the vehicle at ground level the radio also performs well, though as with all VHF and UHF radios, a clear line of sight is best. Battery life is excellent – I took the radio camping for 3 days, using it for several hours each day and did not need to recharge the battery during the trip. Other reviewers have tested the power output, and verified it is putting out the full 5W as advertised on high power. Low power is said to be at 1.8W. See miklor.com’s review.

A feature I enjoy on this radio is the dual display. The radio has two PTT buttons and can be configured to monitor two frequencies simultaneously, and transmit on either frequency using one of the PTT buttons. I prefer to use the “Display Sync” feature, however. This allows the radio to display the channel alpha tag on the top line of the display and the frequency on the bottom line. Pressing either of the PTT buttons will transmit on the single frequency. The GMRS-V1 also has 105 receive-only VHF/UHF channels that can be programmed with any frequency. I like this feature, but I don’t have much saved in these channels other than NOAA weather frequencies. The scan feature on this radio (and many other Chinese radios) is pretty slow and leaves a lot to be desired. I don’t make too much use of this, but the flexibility to store additional RX channels is nice. Rich Carlson of scannermaster.com has a great blog post about (not) using these types of radios as a scammer. Perhaps the most annoying feature of this radio is FM broadcast radio receive capability. This is accessed my pressing a button on the side of the radio, but I noticed I would sometimes accidentally hit this button when I meant to press the monitor button right next to it. Fortunately this feature is easily disabled via the CHIRP programming software.

Overall I’m impressed with this radio. It’s definitely not a cheap toy/bubble pack radio, and offers a great bang for the buck. I’m getting great reception and transmission, I didn’t break the bank, and I won’t be too upset if I smash the radio after wiping out on my bike. Definitely would recommend! Here are some photos of the radio:

I came across this great documentary on map making from 1959 on reddit, but I want to share here as well. This is a really interesting film, showing how topographic maps, globes, and aerial photographs were created 50 years ago:

After work today, I was reading about the throttle response adjustmentprocedure to mitigate turbo lag in the 3.5 EcoBoost F-150. For the non car nerds, I’ll save you a click – it’s just a way to re-calibrate the electronically controlled engine throttle, making it feel more responsive when the gas pedal is pressed. Nearly every part of a car is computer controlled or monitored these days, so I got to wondering…what computer language(s) do Ford and other manufacturers use to write the software that is used by the car’s computer?

Some quick Googling indicated that C is overwhelming used in car electronic control modules. This makes sense as C is very common in embedded systems because it provides easy access to hardware, has low memory usage, and most importantly – it’s fast. Auto manufacturers use a specific implementation of C known asMISRA-C(Motor Industry Software Reliability Association C). MISRA-C is actually a set of guidelines for programming in C that helps avoid bad code which could cause dangerous behavior while a car is in operation. I’m not a C programmer and a lot of this goes over my head, but MISRA-C is just a rigidly defined programming style. When implemented, it will ensure that common errors and pitfalls programmers can make will be avoided entirely when writing software for a car computer.

According to Wikipedia, MISRA-C was originally targeted at the automotive industry, but it has evolved as a widely accepted model for best practices by embedded systems developers in other industries including aerospace, telecom, defense, railway, and others. Pretty cool stuff! If you’re interested, here is some more reading on programming car computers:

Rule 59 (required): The statement forming the body of an “if”, “else if”, “else”, “while”, “do … while”, or “for” statement shall always be enclosed in braces. Basically, this says that from now you must clean up your act, you can’t write sloppy things like the else clause in following example:

if (x == 0)
{
y = 10;
z = 0;
}
else
y = 20;

The idea of this rule is to avoid a classical mistake. In the example below the line z = 1; was added. It looks as though it’s part of the else clause but it’s not! In fact, it is placed after the if statement altogether, which means that the assignment will always take place. If the original else clause would have contained the braces from the beginning this problem would never have occurred.

Working in the GIS field, it’s very common to gather data for a project from various adhoc sources, and often that data is delivered in the form of an Excel spreadsheet. I’ll preface by saying that there’s nothing wrong with delivering data in this way. Excel is a powerful and widely used tool in the business world, and just about everybody who’s ever worked in an office has opened an Excel spreadsheet. But too often in my GIS career I’ve come across projects that are using Excel spreadsheets as a master repository, storing large amounts of tabular data within. It’s not hard to imagine how data integrity can quickly become compromised when people are copying/pasting/emailing/editing/saving spreadsheets, both on their local disk and shared network folders.

So why isn’t Excel a database? It has rows and columns and you can sort data, create formulas, query data with features like VLOOKUP right? While those things may be true, there are several reasons Excel is not a database:

Excel does not allow columns to contain only one specific primitive datatype – integers, floating point decimals, boolean, string, etc. In a database table, each column or field can be constrained to only allow one datatype. Often there will be a column you want to only contain a specific value, like an integer for an ID number. Excel does not provide any data validation, and will not prevent users from entering an invalid value for for the ID. A database table would throw an error, not allowing text to be used for the integer ID column. A database table can also disallow null or empty values for a column, requiring every row to have a value, useful for ensuring each row has an ID number for example. Excel does not provide this functionality.

Excel does not allow multiple users to open and edit the same Excel file. This is a very limiting factor experienced by many users who share files on network drives. I have personally run into this issue quite a few times, having to ask a somebody on the team to close a file that they had open so I could make some edits. Inevitably, myself or somebody else would make a copy of the file to work on locally, and then we’d have issues reconciling the edits each person made with the master copy. A database is designed to allow hundreds or thousands of users to concurrently query, view, and edit the data.

Excel is slooooow. Like really slow. The file size can balloon when there are many rows and columns, many formulas, and special formatting, filters, etc in the worksheets. Sorting worksheets with many rows can be painfully slow, and out of memory errors can happen when the content of the Excel file becomes too large. Databases are designed to maximize performance and offer nearly limitless space, depending on hardware configuration of course. (SQL Server can handle databases of up to 524,272 terabytes!) Excel files should be out of the question when data tables have hundreds of thousands of rows or more or data.

Excel does not allow you to query or join data from multiple tables. Well, it does kinda…features like PivotTables, VLOOKUP,and HLOOKUP can provide functionality similar to some database queries by summarizing data, searching for matching criteria, etc. I won’t get into how to use these features but they do not quite give the same functionality and flexibility as a database provides. A significant limiting factor of Excel is not being able to link or join tables between files – all of these operations must be done with worksheets in the same Excel file. Where Excel really falls short however, is one to many relationships. This is an important concept in data relationships, and these kinds of table joins cannot easily be performed in Excel:

Last, but certainly not least, Excel doesn’t provide any data backup or recovery tools. You may have some automatic file backups on your computer’s hard drive or on a shared network drive, but these may be insufficient if an Excel file is destroyed or altered. A database will have built in features to backup data, and sometimes allow the data to be rolled back to a given point in time. Bringing data back online after a hardware failure is generally an easy process with most database software. A database can also keep logs of all changes to the tables, making it possible to undo a specific table update if an error was made. On a related note, databases will offer options to securely access your data as well. Excel files offer little in the way of protecting the data from unauthorized viewers.

To summarize, Excel is a great tool for data analysis, presentation, and mathematical and statistical calculations. It is a not so great tool for storing large amounts of data. It’s often difficult to maintain data integrity using Excel, especially among multiple users. When the content of the file becomes too large, Excel performance drops significantly making viewing and editing the data difficult.

For any readers out there who currently find themselves in a situation where they feel Excel is not quite the right tool for data storage, I would urge you to explore using a database for your project. There are quite a few options out there, both free and paid, for setting up a database. It’s probably a little beyond the scope of this post to discuss all the various database storage and retrieval types and the specific database software, but since I’m a .NET developer I would suggest trying SQL Server Express. It’s easy to set up a local database server and begin experimenting with migrating data from Excel into database tables. You may also already have Microsoft Access installed on your machine as part of Microsoft Office.

Recently I discovered reddit.com/r/VEDC, a community dedicated to discussing essential tools and supplies one should carry in their vehicle at all times – your “vehicle every day carry.” I made a post in r/VEDC, but I will share it here as well. I like to keep my truck pretty well stocked with tools and supplies that I may need to handle a car emergency, breakdown, or minor injuries. Just about every item in my vehicle inventory has been used, or I was in a situation where I wish I had a certain tool or item so I added it to the collection for the next time. I found some inspiration from the internet as well as from real world experience. Flat tires, dead batteries, and small repairs are common when driving and camping in the Arizona mountains and desert. I need to be able to repair my vehicle, or remain safe until help can arrive. It’s also not uncommon to find a stranded motorist when off-roading, so I like to be able to offer help when possible.

First, the truck – a 2013 Ford F-150 3.5 EcoBoost:

Inventory:

And what isn’t pictured is probably the most important safety item you should be be carrying – water. Living in Arizona this is especially important. I learned this quickly after moving to this state when a serious accident backed up a mountain highway in both directions for miles. It was summer, and highway patrol officers were walking up the highway, handing bottles of water to the motorists. An unplanned extended stay in the desert in the summer time without water and air conditioning can get dangerous fast! So if I’m going to be more than 15 minutes from a Circle K, I’m packing a gallon or two of water just in case.

Posts navigation

Matt Callahan

Welcome to my blog. I am a software developer in Phoenix, AZ and this is my place to post interesting or funny stuff I’ve found about programming, GIS, computers, cars, radios, or whatever. Visit my homepage at mfcallahan.com